Question: How many of William the Silent`s children live to adulthood?
Paraphrase: Count the number of William who made it to the adulthood as the Silent's children life.
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q78454 p:P1971 ?s . ?s ps:P1971 ?obj . ?s pq:P518 wd:Q20483979 }